As an example of the related art, a fuel injection valve is disclosed in PTL 1, in which a valve body including a ball valve opening and closing an injection hole in an injection valve body is slidably incorporated, and between the injection valve body and the valve body, there are provided upper and lower valve guide portions including guide surfaces of the injection valve body, and sliding surfaces of the valve body sliding on the guide surfaces, a stopper of the injection valve body, and a flange of the valve body having an abutment surface formed to make abutment contact with the stopper upon opening the valve body, and in the fuel injection valve, the sliding surfaces on the upper and lower sides of the valve body are formed to have a substantially spherical shape, and clearances between the guide surfaces and the sliding surfaces in the upper and lower valve guide portions are set in a precise fitting condition without rattling.
When the valve body is slightly inclined relative to an inner peripheral surface of a core due to influence of an error in mounting the upper and lower valve guide portions, a sliding surface of a guide ring makes contact with a guide surface of the core, in which the sliding surface has a spherical shape, the guide ring constitutes the valve body, and the guide surface has a smooth shape. That is, the sliding surface of the guide ring has the spherical shape not distorted, and even if the valve body is inclined relative to the guide surface of the core, the guide ring constituting the valve body is slidably held in an axial direction. Thus, abrasion is hardly caused between the guide surface of the core and the sliding surface of the guide ring, and sliding resistance of the valve body can be inhibited from being changed with time. Accordingly, the ball valve as a component member of the valve body has little change in velocity opening and closing a fuel injection hole, and a fuel injection rate can be prevented from being changed with time.
In another example of the related art, a fuel injection valve is disclosed in PTL 2. The fuel injection valve is a fuel injector 1 made up of a nozzle body 2, and in the nozzle body 1, a valve needle 3 is positioned. This valve needle 3 is in operative connection with a valve-closing chain body 4, and this valve-closing chain body 4 cooperates with a valve-seat surface 6 disposed on a valve-seat member 5 to form a sealing seat. The fuel injection valve 1 according to an example illustrated in the figure includes at least one injection opening 7, and can be released inward. The valve-closure member 4 of fuel injector 1 designed according to the present invention which has a nearly spherical form is disclosed.
Thus, an offset-free cardanic valve-needle guidance is achieved, which provides for a precise functioning of the fuel injector 1.